There continues to be a growing demand for semiconductor power devices (i.e., devices capable of carrying large currents at high voltages). Such devices include bipolar transistors, insulated gate bipolar transistors (IGBT), metal oxide semiconductor field effect transistors (MOSFET) and other types of field effect transistors. Notwithstanding significant advances in power device technology, there remains a need for still higher-performing and more cost-effective devices. As the complexity and sophistication of power devices increases, the number of process steps and masks in the manufacturing process also increases, significantly increasing the manufacturing costs. Thus, processing techniques which help reduce the number of process steps and/or masks while maintaining or even increasing the device performance would be desirable.
Furthermore, it is desirable to increase the current density relative to the total die area of a device. One of the limiting factors to higher current ratings is the breakdown voltage, particularly in the edge termination region where array junctions terminate. Because semiconductor junctions include curvatures, numerous techniques are employed to avoid otherwise high concentration of electric field lines. It is conventional in power device design to incorporate edge termination structures with planar field plates along the outer periphery of the device in order to ensure that the breakdown voltage in this region of the device is not any lower than in the active region of the device. However, termination structures (particularly the planar field plate variety) occupy relatively large areas of the die and require additional masking and processing steps, thus resulting in increased costs.
Thus, there is a need for improved power devices with enhanced trench termination structures and cost-effective methods of forming the same.